A binder, its preparation method and application

Abstract

This invention discloses a binder, its preparation method, and its application. The binder comprises the following raw materials: a compound containing soft segments, a compound containing hard segments, and a chain extender. The compound containing soft segments includes polyether polyols and polyester polyols, wherein the polyether polyols are end-capped with amino or hydroxyl groups, and the polyester polyols are end-capped with amino or hydroxyl groups. The compound containing hard segments is a diisocyanate, and the chain extender is a chain extender containing phenolic groups. This binder helps solve the interface problem of the positive electrode during battery operation and is expected to improve the cycle life and stability of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery cathode binders and their preparation technology, and more specifically, relates to a polyurea and / or polyurethane-based binder, its preparation method and application. Background Technology

[0002] As a key component of the positive electrode, the binder maintains electrode integrity by tightly binding the positive electrode material and conductive additives to the current collector, significantly impacting the performance of lithium-ion batteries. However, commonly used binders present several problems. For instance, the mechanism of action of traditional polyvinylidene fluoride (PVDF) binders is based on the physical bonding of van der Waals forces, but this bonding is insufficient to provide enough adhesion to tightly bind the materials together. Furthermore, its low mechanical strength and brittleness make it difficult to maintain the structural integrity of the positive electrode, leading to active material shedding and electrode cracking during battery cycling, resulting in a sharp drop in battery capacity. Therefore, developing lithium-ion battery positive electrode binders with high adhesion and elasticity presents a significant challenge.

[0003] The use of elastomers containing polar groups in binders can effectively bond to the surface of the cathode material through chemical bonds, providing excellent adhesion. Furthermore, the intrinsic mechanical strength and toughness of the elastomer can withstand volume changes on the cathode side during battery operation, preventing electrode cracking and improving battery cycle life. To pursue higher energy density, higher-performance cathode materials such as lithium cobalt oxide and lithium nickel cobalt manganese oxide have emerged. However, due to the catalytic effect of transition metals in these materials, the electrolyte is prone to severe decomposition on the cathode side, leading to various interface problems. Increased interfacial impedance results in severe battery polarization and lower capacity. The dissolution of transition metals into the anode can catalyze the growth of lithium dendrites, leading to risks such as short circuits and thermal runaway, making it difficult to guarantee performance and safety.

[0004] While existing binders have improved mechanical properties, they lack functional designs to address interfacial issues: most products do not consider suppressing electrolyte oxidation side reactions, making it difficult to control CEI layer formation; and they do not fully utilize coordination effects to inhibit transition metal dissolution, failing to fundamentally solve the interfacial instability of the cathode. Therefore, there is an urgent need to develop novel binders to solve these numerous existing problems. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a polyurea and / or polyurethane-based binder, its preparation method, and its application. This binder is an interface-targeted binder that combines elastic coating, antioxidant regulation of the CEI layer, and coordination-based anti-dissolution functions. Specifically, in this binder, the phenolic groups in the chain extender inhibit electrolyte decomposition on the positive electrode side, regulate the formation of the CEI layer, and ensure its uniform growth. Polyether polyols and polyester polyols serve as soft segments, and diisocyanates as hard segments. The soft and hard segments are formed under the action of the chain extender to create the polyurea and / or polyurethane-based binder. The polyether polyol and polyester polyol soft segments synergistically facilitate lithium-ion transport in the positive electrode, while the urea groups and urethane bonds in the hard segments can coordinate with transition metals, preventing their dissolution. This alternating soft and hard segment structure provides the binder with excellent elasticity, helping it to uniformly coat the surface of the positive electrode particles and providing a physical barrier to prevent dissolution with the electrolyte. Furthermore, the preparation method of the binder in this invention is simple, mild, and suitable for large-scale production.

[0006] To achieve the above objectives, according to one aspect of the present invention, a polyurea and / or polyurethane-based adhesive is provided, the adhesive comprising: a compound containing soft segments, a compound containing hard segments, and a chain extender containing phenolic groups. The soft-segment-containing compounds include polyether polyols and polyester polyols, wherein the polyether polyols are capped with amino or hydroxyl groups, and the polyester polyols are capped with amino or hydroxyl groups. The compound containing the hard segment is a diisocyanate.

[0007] According to an embodiment of the present invention, the binder is a polymer formed by chain extension of a condensation prepolymer containing a soft segment and a hard segment compound, using a chain extender.

[0008] According to an embodiment of the present invention, the molar ratio of the polyether polyol and the polyester polyol is (1-3):1; for example, 1:1, 1.5:1, 2:1 or 3:1.

[0009] According to an embodiment of the present invention, the molar ratio of the total amount of the polyether polyol and the polyester polyol to the diisocyanate is 1:(2-3); for example, 1:2, 1:2.5 or 1:3.

[0010] According to an embodiment of the present invention, the molar ratio of the chain extender to the diisocyanate is (0.25 to 0.75):1; for example, 0.25:1, 0.5:1 or 0.75:1.

[0011] According to an embodiment of the present invention, the polyether polyol is selected from at least one of polyethylene oxide, polypropylene oxide, and polytetrahydrofuran. Preferably, the polyethylene oxide, polypropylene oxide, and polytetrahydrofuran are all diamino or dihydroxy-terminated, wherein the number average molecular weight of the polyethylene oxide is 1000 to 4000, for example, one or more of 500, 1000, 2000, or 4000. The number average molecular weight of the polyoxypropylene is 400 to 2000, for example, one or more of 400, 500, 1000 or 2000; The polytetrahydrofuran has a number average molecular weight of 500 to 3000, for example, one or more of 500, 850, 1000, 1500 or 3000; According to an embodiment of the present invention, the polyester polyol is selected from at least one of polycarbonate, polycaprolactone, and O,O'-bis(2-aminopropyl)polypropylene glycol block-polyethylene glycol block-polypropylene glycol (PPEG); preferably, the polyester polyol is end-capped with diamino or dihydroxyl groups. The polycarbonate has a number-average molecular weight of 1000 to 5000, for example, one or more of 800, 1000, 2000, 2500, or 5000; the polycaprolactone has a number-average molecular weight of 500 to 2000, for example, one or more of 500, 800, 1000, 1200, or 2000.

[0012] According to an embodiment of the present invention, the diisocyanate is selected from one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate; According to an embodiment of the present invention, the chain extender is exemplary selected from one or both of divanillin and divanillin ethanolamine.

[0013] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned polyurea and / or polyurethane-based adhesive, the method comprising: performing a polycondensation reaction between a compound containing soft segments and a compound containing hard segments to obtain a prepolymer, and then extending the chain with a chain extender to obtain the adhesive.

[0014] According to an embodiment of the present invention, the method specifically includes the following steps: (1) A compound containing a soft segment and a compound containing a hard segment are mixed in a solvent to carry out a polycondensation reaction to obtain an isocyanate-terminated polyurea prepolymer or an isocyanate-terminated polyurethane prepolymer; wherein, the compound containing the soft segment includes a polyether polyol and a polyester polyol, wherein the polyether polyol is amino- or hydroxyl-terminated, and the polyester polyol is amino- or hydroxyl-terminated; the compound containing the hard segment is a diisocyanate; (2) The prepolymer obtained in step (1) is mixed with the chain extender in a solvent to carry out a chain extension reaction to obtain the binder.

[0015] According to an embodiment of the present invention, the method further includes a post-processing step (3): pouring the chain-extended product obtained in step (2) into a mold, evaporating the solvent and drying it to obtain the post-processed binder.

[0016] According to an embodiment of the present invention, in step (1), the reaction temperature of the polycondensation reaction is 0~70 ℃ and the reaction time is 2~12 h.

[0017] According to an embodiment of the present invention, in step (2), the reaction temperature of the chain extension reaction is 0~70 ℃ and the reaction time is 6~12 h.

[0018] According to an embodiment of the present invention, in step (1), step (2) or step (3), the solvent is the same or different and is selected from at least one of N,N-dimethylformamide, NMP, tetrahydrofuran, and acetonitrile, for example, anhydrous N,N-dimethylformamide.

[0019] According to an embodiment of the present invention, in step (1), the molar ratio of the polyether polyol and the polyester polyol is (1-3):1; the molar ratio of the total amount of the polyether polyol and the polyester polyol to the diisocyanate is 1:(2-3).

[0020] According to an embodiment of the present invention, in step (1), the concentration of diisocyanate in the solvent is 0.1-1.2 mol / L.

[0021] According to an embodiment of the present invention, step (1) specifically involves mixing polyether polyol, polyester polyol and solvent to obtain a polymer solution; then mixing diisocyanate and solvent to obtain a diisocyanate solution; then adding the diisocyanate solution to the polymer solution to carry out a polycondensation reaction to prepare an isocyanate-terminated polyurea prepolymer or polyurethane prepolymer.

[0022] According to an embodiment of the present invention, in step (2), the molar ratio of the chain extender to the remaining diisocyanate in the system after the reaction of step (1) is 1:(1-2).

[0023] According to an embodiment of the present invention, when the adhesive is specifically a polyurethane-based adhesive (i.e., the soft segment used is hydroxyl-terminated), both steps (1) and (2) are carried out under conditions of heating and in the presence of a catalyst, wherein the heating temperature is preferably 25-70 °C, preferably 50-70 °C; and the catalyst is preferably dibutyltin dilaurate.

[0024] Preferably, the catalyst has a total solids content of 0.01-0.5 wt%.

[0025] According to an embodiment of the present invention, when the adhesive is specifically a polyurea-based adhesive (i.e., the soft segment used is amino-terminated), the diisocyanate solution needs to be added to the polymer solution at 0-10°C.

[0026] By employing the above-mentioned preferred mixing sequence, this invention can prevent the rapid reaction of diisocyanate with the amino groups in polyether polyols and polyester polyols to form gels or burst polymerization; it can also fully dissipate the heat released by the reaction of isocyanate groups with amino groups, avoiding overheating of the system and oxidation reaction, which would affect the mechanical properties, electrochemical properties and interface stability of the material.

[0027] According to another aspect of the invention, the invention also provides a positive electrode slurry comprising the above-mentioned polyurea and / or polyurethane-based binder, positive electrode material, conductive carbon, and solvent.

[0028] According to an embodiment of the present invention, the solid content of the positive electrode slurry, calculated as 100% by mass percentage, includes 1-10% of the above-mentioned polyurea and / or polyurethane-based binder, 75-85% of the positive electrode material, and 1-10% of the conductive carbon; the solvent mass is 300-550% of the total solid mass; the solid content refers to the total content of the above-mentioned polyurea and / or polyurethane-based binder, positive electrode material, and conductive carbon being 100%.

[0029] According to an embodiment of the present invention, the cathode material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese oxide (NCM622); According to an embodiment of the present invention, the conductive carbon includes one or more of carbon black, Ketjen black, and SuperP; According to an embodiment of the present invention, the solvent is N-methylpyrrolidone.

[0030] According to another aspect of the invention, the invention provides the application of the above-described polyurea and / or polyurethane-based binder or the above-described positive electrode slurry in energy storage devices.

[0031] Preferably, the energy storage device is a lithium-ion battery or a lithium metal battery.

[0032] Beneficial effects: Existing binders, due to their low adhesion and high brittleness, struggle to ensure the long-term cycle stability of lithium-ion batteries. While using elastomers as binders can enhance cycle performance, they are insufficient to suppress electrolyte decomposition reactions at the positive electrode. This invention addresses this issue by simultaneously incorporating polyether polyols and polyester polyols as soft segments in the binder, synergistically aiding lithium-ion transport at the positive electrode. The urea and urethane bonds in the hard segments can coordinate with transition metals, preventing their dissolution. This alternating soft and hard segment structure provides the binder with excellent elasticity, facilitating uniform coating of the positive electrode particles and providing a physical barrier against electrolyte detachment. Simultaneously, the phenol-containing chain extender inhibits electrolyte decomposition reactions at the positive electrode, ensuring uniform CEI layer growth. Therefore, the polyurea and / or polyurethane-based binder of this invention helps solve the interface problem at the positive electrode during battery operation, potentially improving battery cycle life and stability.

[0033] This invention also regulates the mechanical strength, elasticity, coordination ability, and antioxidant capacity of the binder by using specific amounts of polyether polyols and polyester polyols, diisocyanates, and chain extenders with different structures. Due to the alternating hard and soft segments of polyurea and / or polyurethane, the binder possesses excellent mechanical strength and elasticity, ensuring the mechanical strength and structural stability of the cathode while providing it with toughness against volume expansion during operation. Polyether polyols and polyester polyols have different interactions with lithium ions; polyether polyols interact weakly with lithium ions, which can aid lithium ion migration, while polyester polyols have a stronger coordination ability with lithium ions, which can promote lithium salt dissociation. The synergistic effect of polyether polyols and polyester polyols ensures the lithium ion transport efficiency on the cathode side. Introducing chain extenders containing phenol structures can capture free radicals generated by electrolyte decomposition, terminating unnecessary side reactions and giving the cathode excellent interfacial stability.

[0034] Specifically as follows: 1. The polyurea and / or polyurethane-based binder provided by this invention uses polyether polyol and polyester polyol as soft segments, wherein the polyether segment is soft, the polyester segment has moderate strength, and the isocyanate and chain extender are relatively hard. This strength gradient gives the binder excellent mechanical strength and elasticity. The excellent mechanical strength of the binder can ensure the structural stability of the positive electrode, while the excellent elasticity can ensure that the binder is uniformly coated on the surface of the positive electrode particles, and can also give the positive electrode the ability to resist volume changes, thereby optimizing the battery cycle performance; 2. Traditional binders rely solely on weak van der Waals forces for adhesion, making it difficult to ensure a tight bond between various electrode materials, thus greatly limiting their application in a wide range of materials. The polyurea and / or polyurethane-based binder provided by this invention possesses multiple urethane bonds and / or urea groups, which can form hydrogen bonds with the cathode material, aiding in their tight bonding. Simultaneously, these nitrogen-containing groups provide lone pairs of electrons, which can form coordinate bonds with transition metals in the cathode material, increasing its migration energy barrier and effectively preventing the dissolution of transition metals in high-energy-density materials (cathode materials) such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide, thereby expanding the binder's applicability. 3. Traditional binders are inert binders, providing only adhesion to bond electrode materials, and lack effective means to address interface problems during battery operation. The binder of this invention, by incorporating a phenol-containing chain extender, suppresses side reactions of the electrolyte at the positive electrode interface and promotes uniform growth of the CEI layer. Furthermore, compared to intrinsic modification of the electrode materials, this invention achieves interface stability solely through structural modification of the binder, resulting in a simpler method, lower production costs, and suitability for large-scale production.

[0035] In summary, the polyurea and / or polyurethane-based binder of this invention possesses excellent mechanical and electrochemical properties, and its preparation method is simple and suitable for large-scale production. This binder binds to the cathode material through hydrogen bonding, enhancing adhesion. Simultaneously, its antioxidant capacity stabilizes the cathode-electrolyte interface, thereby effectively improving the cycle stability and lifespan of the cathode material, especially high-energy-density materials containing nickel, cobalt, and manganese. This material has significant application value in the field of energy storage. Attached Figure Description

[0036] Figure 1 The infrared spectrum of the polyurethane adhesive prepared in Example 1 is shown.

[0037] Figure 2 This is a photograph of the polyurethane adhesive prepared in Example 1.

[0038] Figure 3 This is a photograph of the positive electrode sheet prepared in Example 1.

[0039] Figure 4 The intrinsic stress-strain curve of the polyurethane adhesive prepared in Example 1.

[0040] Figure 5 The image shows the 180° peel strength test result of the positive electrode sheet prepared in Example 1.

[0041] Figure 6 The CV curve is for the positive electrode prepared in Example 1.

[0042] Figure 7The CV curves and kinetic fitting results for the positive electrode prepared in Example 1 at different scan rates are shown. Figure 7 (a) in the figure shows the CV curves at different scan rates. Figure 7 (b) in the figure represents the dynamic fitting result.

[0043] Figure 8 The results of long-term cycling of the battery prepared in Example 1 at room temperature and 1C rate.

[0044] Figure 9 The intrinsic stress-strain curves of the polyurethane adhesive prepared in Example 2 and the peel strength test after it was fabricated into a positive electrode sheet are shown. Figure 9 (a) in the figure represents the stress-strain curve. Figure 9 (b) in the figure represents the peel strength test.

[0045] Figure 10 The results of long-term cycling of the battery prepared in Example 3 at room temperature and 1C rate.

[0046] Figure 11 This is a photograph of the positive electrode sheet prepared in Comparative Example 1 after cycling.

[0047] Figure 12 The CV curve is shown for the positive electrode prepared in Comparative Example 2.

[0048] Figure 13 This is a reverse mechanism diagram of the microstructure of the polyurethane adhesive in Example 1 of the present invention.

[0049] Figure 14 This is a SEM image of the surface of the positive electrode prepared in Example 4. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Example 1 Preparation of adhesive: Dihydroxy-terminated polyethylene oxide (1 mmol) with a number-average molecular weight of 2000 and dihydroxy-terminated polycarbonate polyol (1 mmol) with a number-average molecular weight of 2000 were dissolved in 35 mL of anhydrous N,N-dimethylformamide to obtain a polymer solution; dicyclohexylmethane diisocyanate (4 mmol) was dissolved in 5 mL of anhydrous N,N-dimethylformamide to obtain an isocyanate solution; then, the isocyanate solution was added to the polymer solution, and 1-2 drops of dibutyltin dilaurate were added. After reacting at 70 °C for 4 h, an isocyanate-terminated polyurea prepolymer was obtained. Divanillin (2 mmol) was dissolved in 10 mL of anhydrous N,N-dimethylformamide. The resulting divanillin solution was added dropwise to the polyurea prepolymer. After reacting at 70 °C for 12 h, the resulting solution was poured into a polytetrafluoroethylene mold. After the solvent evaporated, a polyurethane adhesive was obtained. Its thickness was controlled to be 0.4–0.8 mm for tensile testing.

[0053] Preparation of positive electrode: Dissolve 0.16 g of polyurethane binder in 6.4 mL of anhydrous N-methylpyrrolidone, add 1.28 g of NCM622 and 0.16 g of Ketjen black, stir for 12 h, pour the resulting slurry onto aluminum foil, and coat it into a film with a scraper, controlling the thickness to be 60-200 μm. Dry it in an oven for 12 h to obtain the positive electrode sheet.

[0054] The chemical structure of the adhesive in Example 1 was verified using Fourier transform infrared spectroscopy, and the results are as follows: Figure 1 As shown, the wave number is 3344 cm⁻¹. -1 The peaks are from the stretching vibrations of NH, which confirms the presence of carbamate bonds; wavenumber range: 2973–2863 cm⁻¹ -1 The peaks are for stretching vibrations of -CH3 and -CH2-, and these signals mainly originate from the soft segments of polyether / polyester polyols and the aliphatic chain moieties of isocyanates; wavenumber 1741 cm⁻¹. -1 The corresponding C=O stretching vibration peak verifies the introduction of polyester polyol components in the soft segment; infrared results indicate that the desired polyurethane adhesive was successfully synthesized.

[0055] Figure 2 This is a photograph of the adhesive used in Example 1. Figure 2 In this process, the difference in polarity between hard and soft segments, as well as the difference in polarity between soft segments, leads to phase separation structures within the material. These structures are smaller than the wavelength of visible light. Furthermore, divanillin is brownish-red, thus the polyurethane adhesive appears as a brown, transparent substance (e.g., ...). Figure 2 (As shown).

[0056] Figure 3 This is a photograph of the positive electrode sheet prepared in Example 1.

[0057] The mechanical properties of the polyurethane adhesive were tested using the following method: The polyurethane adhesive from Example 1 was cut into standard shapes and tested using a universal testing machine. The results are as follows. Figure 4 As shown. From Figure 4 As can be seen from the above, the polyurethane adhesive prepared by the present invention has a mechanical strength of 25.5 MPa and an elongation at break of 1060%, which shows that the polyurethane adhesive has excellent mechanical properties.

[0058] The positive electrode sheet was subjected to a peel strength test. The test method is as follows: The side of the positive electrode sheet coated with the positive electrode material was adhered to a stainless steel sheet with 3M adhesive. The positive electrode sheet was bent 180°. One side of the universal testing machine clamped the tail of the bent positive electrode sheet, while the other side clamped the stainless steel sheet for the peel test. The test results are as follows. Figure 5 As shown. From Figure 5 As can be seen from the above, the average peel strength of the positive electrode sheet prepared using the polyurethane adhesive of the present invention is 1.3 N / cm, which shows that the polyurethane adhesive has excellent adhesion.

[0059] The electrochemical performance of the positive electrode was then characterized using the following method: Several circular samples with a diameter of 14 mm were cut from the positive electrode for later use. A button cell was assembled according to the following structure, and the cyclic voltammetry (CV) curve of the positive electrode was tested: negative electrode shell, gasket, lithium sheet, separator + electrolyte, positive electrode, gasket, spring, positive electrode shell.

[0060] The CV curve of the positive electrode is as follows: Figure 6 As shown in the figure, the test results demonstrate that the positive electrode exhibits excellent redox reversibility in the 2.5-4.5 V range, with complete and highly overlapping redox peaks. This proves that the binder of this invention not only possesses excellent mechanical adhesion, but its unique soft and hard segment structure and functional groups can also significantly optimize interfacial kinetics, suppress side reactions under high voltage, and thus improve the cycle life of the battery. Figure 7 (a) shows the CV curves at different scan rates. Further analysis and fitting yielded the kinetic data in Figure 7 (b). Figure 7 As can be seen from b, the value of b is 0.8761. This value indicates that the positive electrode sheet prepared by the binder of this invention has extremely fast electrode reaction kinetics and significant pseudocapacitive characteristics. This is because the unique microphase separation structure of the polyurethane binder provides a fast channel for lithium ions, effectively overcoming the defect of poor ion conductivity of traditional PVDF binders, thereby significantly improving the rate performance of the battery.

[0061] A button cell was assembled using a positive electrode sheet prepared with polyurethane binder, and charge-discharge tests were conducted. The test results are as follows: Figure 8 As shown, Figure 8 The results show that the electrolyte exhibits excellent cycling stability; after 200 cycles at 1 C at room temperature, the capacity retention is above 95%. Figure 8 ).

[0062] Example 2 Preparation of adhesive: A polytetrahydrofuran (1 mmol) with a number-average molecular weight of 800 and a polycaprolactone (1 mmol) with a number-average molecular weight of 2000 were dissolved in 35 mL of anhydrous N,N-dimethylformamide to obtain a polymer solution. Isophorone diisocyanate (4 mmol) was dissolved in 5 mL of anhydrous N,N-dimethylformamide to obtain an isocyanate solution. Then, the isocyanate solution was added to the polymer solution, and 1-2 drops of dibutyltin dilaurate were added. After reacting at 70 °C for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Divanillin (2 mmol) was dissolved in 10 mL of anhydrous N,N-dimethylformamide. The resulting divanillin solution was added dropwise to the polyurethane prepolymer. After reacting at 70 °C for 12 h, the resulting solution was poured into a polytetrafluoroethylene mold. After the solvent evaporated, a polyurethane adhesive was obtained. Its thickness was controlled to be 0.4–0.8 mm for tensile testing.

[0063] Preparation of positive electrode: Dissolve 0.16 g of polyurethane binder in 6.4 mL of anhydrous N-methylpyrrolidone, add 1.28 g of NCM622 and 0.16 g of Ketjen black, stir for 12 h, pour the resulting slurry onto aluminum foil, coat it into a film with a scraper, control the thickness to be 60-200 μm, and dry it in an oven for 12 h to obtain the positive electrode sheet.

[0064] Mechanical properties of the polyurethane adhesive were tested, and the test results are as follows: Figure 9 As shown, Figure 9 (a) The results show that the polyurethane adhesive material prepared in this embodiment has a mechanical strength of 23.1 MPa and an elongation at break of 916%, exhibiting excellent mechanical properties. The peel strength test results for the positive electrode sheet are as follows: Figure 9 (b) The average peel strength was 1.25 N / cm, indicating that the polycaprolactone soft segment provided good interfacial adhesion.

[0065] The positive electrode sheet prepared using this polyurethane binder was used to assemble a button cell, and charge-discharge tests were conducted. At room temperature, after 200 cycles at 1 C, the capacity retention rate was higher than 91%, indicating that the introduction of the divanillin structure effectively protected the positive electrode interface and improved the cycle stability of the battery.

[0066] Example 3 1.2 mmol of dihydroxyl-terminated polyethylene oxide with a number average molecular weight of 2000 and 0.8 mmol of dihydroxyl-terminated polycarbonate polyol with a number average molecular weight of 2000 were dissolved in 35 mL of anhydrous N,N-dimethylformamide to obtain a polymer solution; 4 mmol of diphenylmethane diisocyanate was dissolved in 10 mL of anhydrous N,N-dimethylformamide to obtain an isocyanate solution; then, the isocyanate solution was added to the polymer solution, and 1-2 drops of dibutyltin dilaurate were added. After reacting at 70 °C for 4 h, an isocyanate-terminated polyurethane prepolymer was obtained. Divanillin (2 mmol) was dissolved in 10 mL of anhydrous N,N-dimethylformamide. The resulting divanillin solution was added dropwise to the polyurethane prepolymer. After reacting at 70 °C for 12 h, the resulting solution was poured into a polytetrafluoroethylene mold. After the solvent evaporated, the polyurethane adhesive was obtained.

[0067] The positive electrode was prepared and tested using the same method as in Example 1. Mechanical testing results showed that the intrinsic mechanical strength of the polyurethane adhesive material was 26.1 MPa and the elongation at break was 980%. The peel strength of the positive electrode was 1.4 N / cm, which is attributed to the strong interaction between the polar groups of polycarbonate and the current collector and active material.

[0068] Figure 10 This is a graph showing the long-cycle results of the battery prepared in Example 3 at room temperature and 1C rate. Figure 10 The results show that the battery prepared with this binder retains more than 92% of its capacity after 200 cycles at 1 C at room temperature. The polyoxyethylene soft segment promotes lithium-ion transport, while the divanillin group inhibits the oxidative decomposition of the electrolyte under high voltage. The synergistic effect of the two significantly improves the overall performance of the battery.

[0069] Example 4 Diamino-terminated polypropylene oxide (PPG) (M n = 400 Da, 1 mmol) and O , O '-Bis(2-aminopropyl)polypropylene glycol block-polyethylene glycol block-polypropylene glycol (PPEG) (M n = 1900 Da, 1 mmol) was dissolved in 35 mL of anhydrous N,N-dimethylformamide to obtain a polymer solution; dicyclohexylmethane diisocyanate (4 mmol) was dissolved in 5 mL of anhydrous N,N-dimethylformamide to obtain an isocyanate solution; then, the isocyanate solution was slowly added dropwise to the polymer solution, and the reaction temperature was maintained at 0-8 °C during the dropwise addition. After reacting at low temperature for half an hour, the reaction was continued at room temperature for 6 h to obtain an isocyanate-terminated polyurethane prepolymer; Divanillin (2 mmol) was dissolved in 10 mL of anhydrous N,N-dimethylformamide. The resulting divanillin solution was added dropwise to the polyurethane prepolymer. The mixture was heated to 60 °C and reacted for 12 h. The resulting solution was then poured into a polytetrafluoroethylene mold. After the solvent evaporated, a polyurea-based adhesive was obtained.

[0070] The positive electrode was prepared and tested using the same method as in Example 1. Mechanical testing results showed that the intrinsic mechanical strength of the polyurea binder material was 37.6 MPa and the elongation at break was 450%. The peel strength of the positive electrode was 1.9 N / cm. Both the mechanical strength and adhesion were higher than those of polyurethane binders, due to the more complete reaction between the amino and cyanate groups and the hydrogen bonds between the urea groups, but this also sacrificed some elongation at break.

[0071] Figure 14 This is a SEM image of the surface of the positive electrode prepared in Example 4. Figure 14 It can be seen that the polyurea-based binder prepared by this invention has excellent mechanical strength, and the electrode surface obtained is continuous and uniform without obvious cracks or powdering marks. It effectively reduces the interfacial impedance and capacity reduction caused by electrode material shedding during cycling. It also has the antioxidant capacity of the divanillin group. The two work together to improve the cycle performance of the battery.

[0072] Comparative Example 1 Dihydroxy-terminated polyethylene oxide (2 mmol) with a number average molecular weight of 2000 was dissolved in 40 mL of anhydrous N,N-dimethylformamide to obtain a polymer solution; dicyclohexylmethane diisocyanate (4 mmol) was dissolved in 10 mL of anhydrous N,N-dimethylformamide to obtain an isocyanate solution; then, the isocyanate solution was added to the polymer solution, and 1-2 drops of dibutyltin dilaurate were added. After reacting at 70 °C for 4 h, an isocyanate-terminated prepolymer was obtained. Divanillin (2 mmol) was dissolved in 5 mL of anhydrous N,N-dimethylformamide and added dropwise to the prepolymer. The reaction continued for 12 h, and the product was dried to obtain a polyurethane adhesive with a single soft segment.

[0073] The binder was tested and found to have a mechanical strength of only 8.5 MPa and an elongation at break of 1280%. Due to the lack of polyester polyols (such as polyester or polycarbonate) as "hard" soft segments and polar anchors, the mechanical strength of the binder was significantly reduced, and the peel strength of the prepared positive electrode was only 0.4 N / cm.

[0074] Figure 11 This is a photograph of the positive electrode sheet prepared in Comparative Example 1 after cycling. Figure 11It can be seen that, during cycling, the active material of batteries assembled using this binder is prone to detaching from the current collector due to insufficient adhesion. Figure 11 This leads to rapid capacity decay. At room temperature, after 100 cycles at 1 C, the capacity retention drops rapidly to 75%, failing to meet the requirements for long-term cycling.

[0075] Comparative Example 2 A polymer solution was obtained by dissolving 1 mmol of dihydroxy-terminated polyethylene oxide (DH2000) and 1 mmol of DH2000 polycaprolactone (DH2000) in anhydrous N,N-dimethylformamide. A polymer solution was obtained by dissolving 4 mmol of dicyclohexylmethane diisocyanate in 5 mL of anhydrous N,N-dimethylformamide. The isocyanate solution was added to the polymer solution, and 1-2 drops of dibutyltin dilaurate were added. The mixture was reacted at 70 °C for 4 h to obtain the isocyanate-terminated prepolymer. 1,4-Butanediol (2 mmol) was used as a common chain extender, dissolved in 5 mL of anhydrous N,N-dimethylformamide, and added dropwise to the prepolymer to continue the reaction for 12 h. After drying, a polyurethane adhesive without functional groups was obtained.

[0076] Although the adhesive has good mechanical properties (mechanical strength 24.0 MPa, elongation at break 1020%) and peel strength (1.2 N / cm), it cannot effectively capture free radicals generated by electrolyte decomposition or suppress interfacial side reactions because the chain extender lacks the phenolic structure unique to divanillin.

[0077] Figure 12 The CV curve of the positive electrode prepared in Comparative Example 2 is shown. Figure 12 It can be seen that the binder exhibits significant oxidation current at high voltages (>4.2V). Batteries assembled using this binder show rapid coulombic efficiency decay during 1C cycling at room temperature, with a capacity retention of only 82% after 150 cycles, demonstrating the crucial role of the divanillin chain extender in improving interfacial stability and cycle life in this invention.

[0078] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polyurea and / or polyurethane based adhesive, characterized in that, The binder comprises the following raw materials: a compound containing soft segments, a compound containing hard segments, and a chain extender containing phenolic groups. The soft-segment-containing compounds include polyether polyols and polyester polyols, wherein the polyether polyols are capped with amino or hydroxyl groups, and the polyester polyols are capped with amino or hydroxyl groups. The compound containing the hard segment is a diisocyanate.

2. The polyurea and / or polyurethane based adhesive according to claim 1, wherein The molar ratio of the polyether polyol to the polyester polyol is (1-3):1; Preferably, the molar ratio of the total amount of the polyether polyol and the polyester polyol to the diisocyanate is 1:(2-3). Preferably, the molar ratio of the chain extender to the diisocyanate is (0.25 to 0.75):

1.

3. The polyurea and / or polyurethane based adhesive according to claim 1, wherein The polyether polyol is selected from at least one of polyethylene oxide, polytetrahydrofuran, and polypropylene oxide; Preferably, the polyester polyol is selected from at least one of polycarbonate, O,O'-bis(2-aminopropyl)polypropylene glycol block-polyethylene glycol block-polypropylene glycol (PPEG), and polycaprolactone.

4. The polyurea and / or polyurethane based adhesive of claim 1, wherein, The diisocyanate is selected from one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

5. The polyurea and / or polyurethane based adhesive of claim 1, wherein, The chain extender is selected from one or more of divanillinol and divanillinolamine.

6. Process for the production of the polyurea and / or polyurethane based adhesive according to any one of claims 1 to 5, characterized in that, The method includes: performing a polycondensation reaction between a compound containing soft segments and a compound containing hard segments to obtain a prepolymer, and then extending the chain with a chain extender to obtain the binder. Preferably, the method specifically includes the following steps: (1) A compound containing a soft segment and a compound containing a hard segment are mixed in a solvent to carry out a polycondensation reaction to obtain an isocyanate-terminated polyurea prepolymer or an isocyanate-terminated polyurethane prepolymer; wherein, the compound containing the soft segment includes a polyether polyol and a polyester polyol, wherein the polyether polyol is amino- or hydroxyl-terminated, and the polyester polyol is amino- or hydroxyl-terminated; the compound containing the hard segment is a diisocyanate; (2) The prepolymer obtained in step (1) is mixed with the chain extender in a solvent to carry out a chain extension reaction to obtain the binder.

7. The preparation method according to claim 6, characterized in that, In step (1), the reaction temperature of the polycondensation reaction is 0~70 ℃, and the reaction time is 2~12 h; Preferably, in step (2), the reaction temperature of the chain extension reaction is 0~70 ℃ and the reaction time is 6~12 h; Preferably, in step (1) or step (2), the solvents are the same or different and are selected from at least one of N,N-dimethylformamide, NMP, tetrahydrofuran, and acetonitrile; Preferably, in step (1), the concentration of diisocyanate in the solvent is 0.1-1.2 mol / L; Preferably, in step (2), the molar ratio of the chain extender to the remaining diisocyanate in the system after the reaction of step (1) is 1:(1-2).

8. The preparation method according to claim 6, characterized in that, When the adhesive is specifically a polyurethane-based adhesive, both steps (1) and (2) are carried out under conditions of heating and in the presence of a catalyst, wherein the heating temperature is 20 to 70°C; and the catalyst is dibutyltin dilaurate.

9. A positive electrode slurry, characterized in that, It includes the polyurea and / or polyurethane-based binder, positive electrode material, conductive carbon, and solvent as described in any one of claims 1-5; Preferably, the solid content of the positive electrode slurry, calculated as 100% by mass percentage, includes 1-10% of the above-mentioned polyurea and / or polyurethane-based binder, 75-85% of the positive electrode material, and 1-10% of the conductive carbon; the solvent mass is 300-550% of the total solid mass; the solid content refers to the total content of the above-mentioned polyurea and / or polyurethane-based binder, positive electrode material, and conductive carbon being 100%.

10. The use of the polyurea and / or polyurethane-based adhesive according to any one of claims 1-5 in energy storage devices; Preferably, the energy storage device is a lithium-ion battery or a lithium metal battery.

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